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Regulation of gut function varies with life-history traits in chuckwallas (Sauromalus obesus: Iguanidae)

Tracy, Christopher R. and Diamond, Jared (2005). Regulation of gut function varies with life-history traits in chuckwallas (Sauromalus obesus: Iguanidae). Physiological and Biochemical Zoology,78(4):469-481.

Document type: Journal Article
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IRMA ID 78672763xPUB27
Title Regulation of gut function varies with life-history traits in chuckwallas (Sauromalus obesus: Iguanidae)
Author Tracy, Christopher R.
Diamond, Jared
Journal Name Physiological and Biochemical Zoology
Publication Date 2005
Volume Number 78
Issue Number 4
ISSN 1537-5293   (check CDU catalogue  open catalogue search in new window)
Start Page 469
End Page 481
Total Pages 13
Place of Publication Chicago, IL, United States
Publisher The University of Chicago Press
Field of Research 0606 - Physiology
0608 - Zoology
1116 - Medical Physiology
HERDC Category C1 - Journal Article (DEST)
Abstract We examined the effects of hibernation and fasting on intestinal glucose and proline uptake rates of chuckwallas (Sauromalus obesus) and on the size of organs directly or indirectly related to digestion. These lizards show geographic variation in body size and growth rate that parallels an elevational gradient in our study area. At low elevation, food is available only for a short time during the spring; at high elevation, food may also be available during summer and autumn, depending on rainfall conditions in a given year. We hypothesized that low-elevation lizards with a short season of food availability would show more pronounced regulation of gut size and function than high-elevation lizards with prolonged or bimodal food availability. Hibernating lizards from both elevations had significantly lower uptake rates per milligram intestine for both nutrients, and lower small intestine mass, than active lizards. The combination of these two effects resulted in significantly lower total nutrient uptake in hibernating animals compared to active ones. The stomach, large intestine, and cecum showed lower masses in hibernators, but these results were not statistically significant. The heart, kidney, and liver showed no difference in mass between hibernating and nonhibernating animals. Lizards from low elevations with a short growing season also showed a greater increase in both uptake rates and small intestine mass from the hibernating to the active state, compared to those from high elevations with longer growing seasons. Thus, compared to those from long growing season areas, lizards from short growing season areas have equal uptake capacity during hibernation but much higher uptake capacity while active and feeding. This pattern of regulation of gut function may or may not be an adaptive response, but it is consistent with variation in life-history characteristics among populations. In areas with a short season, those lizards that can extract nutrients quickly and then reduce the gut will be favored; in areas where food may be available later in the year, those lizards that maintain an active gut would be favored. While other researchers have found much greater magnitudes of gut regulation when making comparisons among species, we find the different patterns of change in gut function between different populations of chuckwallas particularly intriguing because they occur within a single species.
DOI http://dx.doi.org/10.1086/430232   (check subscription with CDU E-Gateway service for CDU Staff and Students  check subscription with CDU E-Gateway in new window)


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